Brokeback Mountain stars Heath Ledger and Michelle Williams have split up, say reports.

Friends of the pair have claimed that their hectic acting schedules have caused them to drift apart and that they are now calling a halt to their relationship.

An insider told People magazine: "It was rocky for a while. They did what they could to make it work."

The Dawson's Creek actress gave birth to the couple's daughter Matilda back in 2005. The pair got engaged in 2004 after initially meeting on the set of Brokeback Mountain.